MX2012009020A - Can body. - Google Patents

Abstract

A drawn and ironed metal can body adapted for seaming onto a can end, the can body comprising: - an ironed sidewall - an enclosed, undomed base integrally formed with the sidewall, a bottom panel of the base having an average Rockwell hardness number that is at least approximately 64.

Description

CAN BODY FIELD OF THE INVENTION This invention relates to containers, and more particularly to metal containers for food, beverages, aerosols, and the like formed from a metal foil.

BACKGROUND OF THE INVENTION Two-piece metal containers for food and beverages are often manufactured by wall-stretching and ironing processes (DWI, also referred to as ironing and stretching (D &I)) or stretching and re-stretching (DRD). The term "two pieces" refers to i) the cup section and ii) the closure that would later be attached to the open end of the cup section to form the container.

In a DWI (D &I) process (as illustrated in Figures 6 to 10 of U.S. Patent Number 4,095,544), a flat (typically) circular preform stamped from a roll of foil is stretched to through a drawing die, under the action of a punch, to form a first surface cup stage. This initial stretching step does not result in any intentional thinning of the preform.

Thereafter, the cup, which is typically mounted on the end face of a tamper or tight-fitting punch, is pushed through one or more annular wall ironing dies for the purpose of effecting a reduction in the thickness of the side wall of the cup, thus resulting in an elongation in the side wall of the cup. By itself, the ironing process will not result in any change in the nominal diameter of the cup in the first stage.

Figure 1 shows the distribution of metal in a container body resulting from a conventional D I process (D &I). Figure 1 is illustrative only, and is not intended to be scaled exactly. Figure 1 shows three regions where: i. Region 1 represents the non-ironed material of the base. This remains approximately the same thickness as the incoming caliper of the preform, that is, it is not affected by separate manufacturing operations of a conventional DWI process. ii. Region 2 represents the ironed middle section of the side wall. Its thickness (and therefore, the amount of ironing required) is determined by the performance required for the body of the container. iii. Region 3 represents the upper ironed section of the upper wall. Typically in the making of cans, this ironed upper section has approximately 50-75% of the thickness of the incoming gauge.

In a DRD process (as illustrated in Figures 1 to 5 of US 4,095,544), the same stretch technique is used to form the first stage cup. However, instead of employing an ironing process, the first stage cup is then subjected to one or more re-stretching operation which act to progressively reduce the diameter of the cup and thus elongate the side wall of the cup. By themselves, more conventional re-stretching operations are not intended to result in any change in the thickness of the cup material. However, taking the example of container bodies manufactured from a typical DRD process, in practice there is typically some thickening in the upper part of the finished container body (of the order of 10% or more). This thickening is a natural effect of the re-stretching process and is explained by the sympathetic effect on the material when the re-stretching of a large diameter to a smaller diameter cup is performed.

Note that there are known alternative DRD processes that achieve a reduction in thickness in the side wall of the cup through the use of small or compound radius stretching dies to thin the side wall by extending the stretching and re-stretching steps.

Alternatively, a combination of ironing and re-stretching may be used in the cup of the first stage, which then reduces both the diameter of the cup and the thickness of the side wall. For example, in the field of the manufacture of two-piece metal containers (cans), the container body is typically made by stretching a preform into an intermediate first stage cup and subjecting the cup to a number of re-operation operations. Stretching until reaching a container body of the desired nominal diameter, then followed by ironing the side wall to provide the desired thickness and height of the side wall.

However, DWI (D &I) and DRD processes used on a large commercial scale do not act to reduce the thickness (and subsequently the weight) of the material at the base of the cup. In particular, stretching does not result in a reduction in the thickness of the object being stretched, and ironing only acts on the side walls of the cup. Essentially, for DWI (D &I) and DRD processes for the manufacture of cups for two-piece packages, the thickness of the base remains relatively unchanged from that of the incoming caliper of the preform. This may result in the base being thicker than required for performance purposes.

Food, beverages and other products are often packaged in two-piece cans made of aluminum, tinned steel, or coated steel sheets. The two-piece cans include a can body having an integral base and a side wall and a lid that is sewn to the top of the side wall of the can body.

Tin plate for can making is typically provided under ASTM A623 or ASTM A624 specifications. Although most commercial tinplate is not hot rolled or annealed later in the manufacturing process, often a cold rolling process of the surface provides an identifiable grain direction. The commercial tinplate grains for can making are not of equal axes, but rather, in a cross-sectional sample, they define a longitudinal direction, which defines the grain direction, and a transverse direction. Grain boundaries are visible at the time of enlargement through widely accepted techniques, as described in ASTM E 112.

Aluminum for can making often begins as a sheet of aluminum alloy 3104-H19 or 3004-H19, said aluminum with approximately 1% manganese and 1% magnesium for strength and malleability. The cold rolling process used to produce commercial grade aluminum for can making produces a metal sheet that has grain structures without equal axes. In this aspect, the grains of the aluminum sheet define a longitudinal direction and a transverse direction. Due to the amount of cold rolling, the grains in the commercial aluminum foil for can making are elongated compared to commercial tinplate grains for can making.

There is a need for an improved technology of improved cans and cans that makes efficient and effective the use of sheet material that takes advantage of the economy of the metal supply.

SUMMARY OF THE INVENTION A can body is formed from a process that includes a spreading operation on the metal that becomes at least a portion of the base, and then stretching the material radially outwardly, preferably toward the side wall. The subsequent ironing of the side wall produces cans having desired base and wall thicknesses from the less expensive and thinner metal sheet. In this regard, additional rolling steps do not need to be executed on the metal sheet in the laminator, but the metal can be thinned during the can making process to achieve the desired attributes. The can bodies formed from this method may have attributes that are, unlike cans, made from thinner, less economical tinplate. For example, the reduction of the thickness and distribution of the raw sheet, the increase in hardness due to the paving operation, and the change of the microgram structure due to the spread may be unique in the base of the formed can body. from the disclosed method.

Said stretched and ironed metal can body that is adapted to be sewn onto a can end includes a flat ironed side wall and a non-domed base, enclosed integrally formed with the side wall. The bottom panel of the base (i.e., the portion of the base within the peripheral sausage) can preferably have an average Rockwell hardness number that is at least about 64. The average is a numerical average of points taken through the center and in the laminate direction. The average Rockwell hardness number can be between 64 and 70. These hardness numbers are based on a process starting with conventional continuously hardened sheet T4 having an initial hardness of 58. However, the present invention is not limited to starting with some thickness or hardness of particular sheet.

Preferably, the side wall of the can body has an average thickness of between about 0.006 inches (0.015 centimeters) and 0.015 inches (0.038 centimeters), and the side wall has a flange with the ability to be double stitched to a curvature of a can end.

According to another embodiment or aspect of the present invention, the base of the can body can have (i) a Rockwell hardness that is at least about 65 or (ii) an average change in hardness of the raw sheet of at least 5 in Rockwell hardness number or (iii) an average change in Rockwell hardness number of the raw sheet of at least 7%. Preferably, the increase in the average Rockwell hardness number is between 5 and 17, and may also be between 6 and 15, or 7 and 12, or 8 and 10. Preferably, the increase in average Rockwell hardness number , without considering the start page, - it is between 8% and 21%, and preferably between 10% and 16%, or between 12% and 15%. The side wall of all the cans referenced in the summary section preferably has a thickness between about 0.004 and about 0.015. inches (0.010 and 0.038 centimeters), and more preferably between approximately 0.004 inches and 0.007 inches (0.010 and 0.017 centimeters).

According to another embodiment or aspect of the present invention, the base of the can body is formed of a sheet that is at least 0.105 inches thick and includes an ironed side wall and an integrally formed base with the side wall . The base includes a peripheral sausage and a substantially flat bottom panel having an average thickness between 0.006 and 0.015 inches (0.015 and 0.038 centimeters) and an average decrease in thickness of the raw sheet of at least 2%. Preferably, the average decrease in thickness of the raw sheet is between 5% and 30%, or between 10% and 25%. Preferably, the average lower panel thickness is between 0.008 and 0.012 inches (0.020 and 0.030 centimeters) or between 0.008 and 0.010 inches (0.020 and 0.025 centimeters).

According to another embodiment or aspect of the present invention, the base of the can body is non-vaulted and includes a flattened side wall and a peripheral sausage and a lower wall radially within the sausage. The grains in the tinplate of the base have an average aspect ratio of at least 1.4, preferably between 1.5 and 2.5, or between 1.6 and 2.2, or approximately 1.8. Preferably, the average aspect ratio is at least 20% greater than the average aspect ratio of the blank sheet from which the can body is formed, and preferably between 20% and 100%, between 30 and 30%. % and 70%, or between 40% and 60%, without considering the starting sheet material.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a side elevational view of a prior art container body that is the result of a conventional DWI process. This shows the distribution of the material in the base and lateral wall regions of the container body.

Figure 2 is a graph showing in general terms the manner in which the overall net cost of manufacturing a typical two-piece metal container varies with the incoming caliper of the metal sheet. The graph shows how the reduction of the thickness of the sidewall region (for example, by ironing) has the effect of bringing the net overall cost down.

Figure 3 is a graph corresponding to Figure 2, but based on the actual price data for tinplate supplied by the UK.

The embodiments of the invention are illustrated in the following figures, with reference to the accompanying description: Figure 4 is a graphical representation of the variation in the thickness of the base of a cup that results from the use of an "extended" punch (according to the invention) having a domed profiled end face.

Figure 5a is a side elevational view of the tools of a picking press used to form a cup of the first stage from a sheet metal preform. The figure shows the tools before the initial drawing operation started.

Figure 5b corresponds to Figure 5a, but upon completion of the initial drawing operation to form the cup of the first stage.

Figure 6a is a side elevational view of a paving rig used to execute the paving operation of the invention. The figure shows the paving rig before the paving operation started.

Figure 6b shows the paving rig of figure 6a, but upon completion of the paving operation.

Figure 7 shows an alternative embodiment of that of Figures 6a and 6b, in which the pre-extended cup is clamped around its side wall for the spreading operation.

Figure 8 shows an alternative embodiment of the extension punch to that shown in Figures 6a and 6b.

Figure 9 shows a further alternative embodiment of the extension punch to those shown in Figures 6a, 6b and 8, where the end face of the spread punch includes various relief features.

Figures 10a-d show perspective views of a body-forming assembly used to re-stretch the extended cup. The figures show the operation of the body shaper from the beginning until the completion of the stretching operation.

Figure 11 shows a detailed view of the re-stretching die used in the body-forming assembly of Figures 10A-d.

Figure 12 shows the sheet metal preform in various stages during the method of the invention as it moves from a flat sheet to a finished cup.

Figure 13a is a side elevational view of a paving rig used to execute the paving operation of the invention. The figure shows - the paving rig before the paving operation has begun.

Fig. 13b shows the paving rig of Fig. 13a, but upon completion of the paving operation.

Figure 14 shows an alternative embodiment of an extension punch to that shown in Figures 13a and 13b.

Figure 15 shows a further alternative embodiment of an extension punch to that shown in Figures 13a and 13b, where the end face of the spread punch includes various relief features.

Figure 16 shows an expansion of the metal foil in which the paving operation of the invention has been executed on a plurality of "enclosed portions" separated from each other and placed through the area of the metal foil.

Figures 17a and 17b show the manner in which, when executing the spreading operation to provide the extended sheet shown in Figure 16, any simultaneous spreading of two or more of the enclosed portions may be stepped to reduce the loads imposed on them. used tools.

Figure 18a is a side elevation view of the tools of a picking press used to execute an initial drawing step of the drawing operation to form a cup from the extended metal sheet. The figure shows the tool before this initial stretching step has begun.

Figure 18b corresponds to Figure 18a, but upon completion of the initial drawing step.

Figure 19 shows a metal sheet preform in various stages during the method of the invention as it proceeds from a flat sheet to a finished cup.

Figure 20 shows the use of the cup of the invention as part of a two-piece package.

Figure 21 is a graph of hardness and thickness of a cup and an indication of the location of measurements in the cup, formed in accordance with an aspect of the present invention.

Fig. 22 is a base of a can body formed from the cup shown in Fig. 21, with numbered locations corresponding to the numbered locations shown in the cup of Fig. 21.

Figure 23 is a micrograph of the grain structure of a conventional cup and can body base.

Figure 24 is a micrograph of the grain structure of a can body cup and base formed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION The following describes two exemplary methods for forming a cup from which a can body according to the present invention can be formed, as well as the can cup and body. In the first method, an extension operation is executed in a stretched cup, followed by a re-stretching operation. In the second method, an extension operation is executed on a flat preform, followed by a stretching operation. Preferably, the wall of a cup formed through the method is ironed to have the finished can body. The invention of the present can body or finished can is not limited to the particular steps described below. Rather, the steps of producing the can structure are described to illustrate possible ways of achieving the attributes of the cup or can body. According to a first method for forming an intermediate cup, a pick-up press 10 has a drawing pad 11 and a drawing die 12 (see Figures 5a and 5b). A drawing drill 13 is co-axial with the drawing die 12, as indicated by a common axis 14. A circumferential cutting element 15 surrounds the drawing pad 11.

In use, a flat section of the metal sheet 20 is held in position between opposite surfaces of the drawing pad 11 and the drawing die 12. Steel plate (Temple 4) with an incoming gauge thickness (tensile) of 0.280 millimeters it has been used for the metallic foil 20. However, the invention is not limited to particular gauges or metals. The metal foil section 20 is typically cut from a roll of foil (not shown). After the section of the metal sheet 20 has been placed, the circumferential cutting element 15 is moved downwards to cut a circular flat preform 21 of the metal sheet (see Figure 5a). The excess material is indicated by 22 in Figure 5a.

After the preform 21 has been cut from the sheet 20, the stretching punch 13 is moved axially downwardly through the stretching die 12 to progressively stretch the flat preform against the forming surface 16 of the drawing die 12 towards the profile of a cup 23 having a side wall 24 and an integral base 25. This drawing operation is shown in Figure 5b, and includes a separate view of the stretched cup 23 when it is removed from the press 10. In Figure 5a includes a detailed view of the radius Ri2 at the junction between the end face of the drawing die 12 and its forming surface 16. As for conventional drawing operations, the radius R12 and the load applied by the drawing pad 11 to the periphery of the preform 21 are selected to allow the preform to slide radially inwardly between the opposite surfaces of the stretching pad 11 and drawing die 12 and along or of the forming surface 16 as the stretching punch 13 moves progressively downward to stretch the preform in the cup 23. This ensures that the preform 21 is predominantly stretched, instead of being stretched (thinned) (or worse , twisted around the junction between the end face of the drawing die and the forming surface). Depending on the size of the radius Ri2 and, to a lesser extent, the severity of the clamping load applied by the stretching pad 11, the thickness of the wall of the cup 23 will remain essentially unchanged from that of the incoming caliper of the preform 21. , that is, an insignificant spreading or thinning should occur. However, in alternative embodiments of the invention, it is permissible for the load applied by the stretching pad 11 to suffice that a combination of stretching and stretching occurs under the action of the stretching punch 13. The cup 23 resulting from this Initial stretch operation is also referred to as "first stage cup".

Spreading operation, first illustrative method Following the initial stretching operation shown in Figures 5a and 5b, the stretching cup 23 is transferred to an extension 30, an example of which is illustrated in Figures 6a and 6b. The paving rig 30 has two plates 31, 32 which are movable relative to each other along the parallel axes 33 under the action of loads applied through cylinders 34 (see figures 6a and 6b). The fillers can be applied by any conventional means, for example, rheumatically, hydraulically or through high pressure nitrogen cylinders.

On the plate 31 is mounted an extension punch 35 and a fastening element in the form of an annular clamping ring 36. The annular clamping ring 36 is located radially outwardly of the spreading punch 35. The spreading punch 35 it is provided with a domed end face (see figures 6a and 6b).

A cup holder 37 is mounted on the plate 32. The cup holder 37 is a tubular insert having an annular end face 38 and an outer diameter corresponding to the internal diameter of the stretching cup 23 (see figures 6a and 6b). . In use, the stretching cup 23 is mounted on the cup holder 37 so that the annular end face 38 contacts a corresponding annular region 26 in the base 25 of the cup (see figures 6a and 6b). The loads are applied through the cylinders 34 to move the plates 31, 32 together along the axes 33 until the annular region 26 is firmly clamped in an annular manner between the flat surface of the clamping ring 36 and the annular end face 38 of cup holder 37. Clamped annular region 26 defines an enclosed portion 27 of the cup. In the embodiment shown in Figures 6a and 6b, the annular holder then separates the base 25 into two discrete regions: the clamped annular region 26 and the enclosed portion 27.

The spreading drill 35 is then moved axially through the clamping ring 36 to progressively deform and extend (thin) the enclosed portion 27 in a domed profile 28.

In the embodiment shown in the figures, the enclosed portion 27 is domed inwardly 28 in the cup (see Figure 6b). However, in an alternative embodiment, the enclosed portion 27 may then be domed outwardly of the cup.

Ideally, the clamping loads applied during this paving operation are sufficient to ensure that little or no material from the clamped annular region 26 (or the side wall 24) flows into the enclosed portion 27 during paving. This helps to maximize the amount of spreading and thinning that occurs in the domed region 28. However, as indicated above in the general description of the invention, it has been found that the spread and thinning of the enclosed portion 27 can continue to occur when a limited amount of material flow is allowed from the clamped annular region 26 (or from outside the clamped region) in the enclosed portion.

In summary, this paving operation and the resultant thinning of the base 25 is critical to achieve the manufacture of a cup or container body having a base thickness that is less than that of the incoming caliper of the metal sheet.

In an alternative embodiment shown in Figure 7, the side wall 24 instead of the base 25 is held during the spreading operation. Figure 7 shows an annular region 26 of the side wall adjacent to the base that is being held between the cup holder 370 and the holding member 360. Either or both of the cup holder 370 and the holding member 360 can be segmented to facilitate the attachment of the side wall, and accommodate cups of different sizes. The annular fastening of the side wall 24 defines a portion enclosed 27 inwardly of the clamped annular region 26 (see Figure 7). An extension punch 35 is also indicated in Figure 7. Note that the other features of the spreading rig are excluded from Figure 7 for ease of understanding.

In a further alternative embodiment, the single extension punch 35 is replaced by a punch assembly 350 (as shown in Figure 8). The drill assembly 350 has: i) a first group 351 of an annular piercing element 351a surrounding a central core piercing element 351b; Y ii) a second group 352 of an annular piercing element 352a.

For ease of understanding, Figure 8 only shows the punch assembly 350 and the stretched cup 23. Although not shown in Figure 8, in use an annular region 26 of the base 25 of the cup would be held during the spreading operation. in a manner similar to the embodiment shown in Figures 6a and 6b.

In use, the first and second groups of punch elements 351, 352 face the opposing surfaces of the enclosed portion 27. The spreading operation is performed by moving the first and second groups of punch elements 351, 352 together to deform and extending (thinning) the enclosed portion 27. The enclosed portion 27 is deformed into an undulating profile 280 (see Figure 8).

In a further embodiment, a single extension punch 35 has a number of relief features in the form of cavities / cuts 353 provided on its end face (see Figure 9). In the embodiment shown, there is a central cavity / cut surrounded by a single annular cavity / cut. However, alternative configurations of the cavity / cut can be used.

Operation of (re) stretched in extended cup For the embodiment of the invention shown in Figures 6a and 6b, the extended cup with its domed and thinned region 28 in the base is transferred to a body forming assembly 40 (see Figures 10a and 10d). The body former assembly 40 comprises two halves 41, 42 (indicated by the arrows in Figures 10a to 10d).

The first half 41 of the body forming assembly 40 has a tubular re-stretching drill 43 mounted on the same axis as the circumferential holding ring 44. As can be seen from Figures 10a to 10d, the clamping ring 44 circumferentially surrounds the re-stretching punch 43 such as a sleeve. As will be understood from the following description and looking at Figures 10a to 10d, the re-stretching punch 43 is movable through and independently of the circumferential clamping ring 44.

The second half 42 of the body forming assembly 40 has a re-stretching die 45. The re-stretching die 45 has a tubular portion having an outer diameter corresponding to the internal diameter of the extended cup 23 (see Figure 10a) . The re-stretching die 45 has a forming surface 46 on its inner axial surface, which ends in an annular end face 47 (see Figures 10a to 10d). The annular end face 47 of the re-stretching die 45 corresponds in width to that of the annular region 26 on the base of the extended cup.

In use, the extended cup 23 is first mounted on the re-stretching die 45 (as shown in Figure 10a). Then, as shown in Fig. 10b, the two halves 41, 42 of the body-forming assembly 40 are moved axially relative to each other so that the annular region 26 of the base of the extended cup is clamped between the face of the body. annular end 47 of the re-stretching die 45 and the surface of the circumferential holding ring 44.

Once clamped, the re-stretching punch 43 is then forced axially through the clamping ring 44 and the re-stretching punch 45 (see arrow A in Figures 10c and 10d) to progressively re-stretch the material from the cup extending along the forming surface 46 of the re-stretching die. The use of the re-stretched drill 43 and the die 45 has two effects: i. causing the material of the side wall 24 to be drawn radially inwardly and then axially along the forming surface 46 of the re-stretching die 45 (as indicated in arrows B of Figures 10c and 10d). In this way, the cup is reduced in diameter (as indicated by the comparison of Figure 10a with Figure 10); Y ii. causing the stretched and thinned material in the domed region 28 of the base to be progressively pulled out and transferred from the base to the reduced diameter side wall (as indicated in arrows C of Figures 10c and lOd). This has the effect of flattening the domed region 28 of the base (see especially Figure 10).

Figure 10 shows the final state of the re-stretched cup 23 when the re-stretching punch 43 has reached the end of its stroke. It can clearly be seen that the previously domed region 28 of the base has been pulled essentially flat to provide a cup body or container 23 where the thickness of the base 25 is thinner than the incoming preform 21. As indicated previously, this reduced thickness in the base 25 - and consequent weight reduction - is enabled by the previously executed paving operation.

As shown in the detailed view of the re-stretching die 45 in Figure 11, the crossing between the forming surface 46 and the annular end face 47 of the re-stretching die is provided with a radius R 5 in the range from 1 to 3.2 millimeters. The provisioning of a radius R45 lightens the corner of another sharp shape that would be present at the junction between the forming surface 46 and the annular end face 47, and thus reduces the risk that the metal of the extended cup 23 will tear when It is re-stretched around this junction.

Note that although Figures 10a to 10d show the use of a tubular re-stretcher 43 having an annular end face, the piercer alternatively can have a closed end face. The closed end face can be profiled to press a corresponding profile at the base of the cup.

The drawing operation described above and illustrated in Figures 10a to 10d is known as reverse re-stretching. This is because the re-stretching punch 43 is directed to reverse the profile of the spread cup. In effect, the re-stretched hole reverses the direction of the material and flips the extended cup. This can be seen by comparing the cup profiles of Figures 10a to lOd. The reverse re-stretching of the cup in this context has the advantages of: i. preventing uncontrolled buckling of the domed region 28 from the base of the extended cup (especially when using a re-stretching punch having a closed end face); Y ii. maximize the transfer of material from the domed region 28 to the side walls 24.

Note that although the embodiment shown in Figures 10a to 10d illustrates the inverse re-stretching, conventional re-stretching would also work; that is, where the re-stretching drill acts in the opposite direction to reverse the re-stretching and not to overturn the cup.

Figure 12 shows the changes experienced by the metal preform 21 from: a) before any training operations are carried out, until b) forming the cup of the first stage in the cupping press 10, until c) the extended and thinning operation executed on the paving rig 30, until d) the re-stretched cup that results from the body forming assembly 40.

A location on the domed region 28 of the extended cup is indicated as X in Figure 12. The figure illustrates the effect of the re-stretching operation by radially pulling X to X '. The figure shows that the base of the cup at that location after the extended (textendido) (and after the re-stretched operation) has a reduced thickness in relation to the incoming caliber of the incoming preform 21 ^, ie textendido < Tentrante- As previously observed, this thinning of the base is enabled by the paving operation.

In order to maximize the height of the side wall 24 of the cup with its thinned base, the re-stretched cup can also undergo ironing of the side walls as it is stretched through a succession of ironing dies (not shown). ). This ironing operation has the effect of increasing the height and decreasing the thickness of the side wall, and thus maximizing the volume enclosed in the cup.

Spreading operation, first illustrative method According to a second method for orming the intermediate cup shown in Figs. 6a to 6b, a flat section of metal foil 10 'is located within a spread 20' (an example thereof is illustrated in Figs. 13a and 13b). The steel plate (temper 4) with a gauge thickness of input (tenter) of 0.280 millimeters has been used for the metal foil 10 '. However, the invention is not limited to particular gauges or metals. The section of the metal foil 10 'is typically cut from a roll of foil (not shown). The extension rig 20 'has two plates 21', 22 'which are movable in relation to each other along parallel axes 23' under the action of loads applied through the cylinders 24 '(see FIGS. 13a and 12a). 13b). The fillers can be applied by any conventional means, for example pneumatically, hydraulically or by means of high pressure nitrogen cylinders.

On the plate 21 'an extension punch 25' and a clamping element in the form of a first clamping ring 26 'are mounted. The first clamping ring 26 'is located radially outwardly of the spreading drill 25'. The extension punch 25 'is provided with a domed end face (see figures 13a and 13b).

A second clamping ring 27 'is mounted on the plate 22'. The second clamping ring 27 'is a tubular insert having an annular end face 38' (see Figures 13a and 13b). In use, the loads are applied through the cylinders 24 'to move the plates 21', 22 'relative to one another along the axes 23' until the flat section of the metal sheet 10 'is firmly clamped in a manner ring between the first and second clamping rings 26 ', 27' to define an annular region clamped 15 'in the section of the metal sheet. The clamped annular region 15 'defines a portion enclosed 16' in the metal foil 10 '.

The spreading drill 25 'is then moved axially through the first clamping ring 26' to progressively deform and extend (thin) the metal of the enclosed portion 16 'in a domed profile 17' (see Figure 13b).

Ideally, the clamping loads applied during this paving operation are sufficient to ensure that little or no material from the clamped annular region 15 'flows into the enclosed portion 16' during paving. This helps to maximize the amount of spreading and thinning that occurs in the enclosed portion 16 '. However, as indicated above in the general description of the invention, it has been found that the spread and thinning of the metal of the enclosed portion 16 'may continue to occur when a limited amount of material flow is allowed from the annular region secured 15 '(or from outside the region fastened) in the enclosed portion.

In an alternative embodiment, the single extension punch 25 'is replaced by a punch assembly 250' (as shown in Figure 14). The drill assembly 250 'has: i. a first group 251 'of an annular piercing element 251a' surrounding a central core piercing element 251b '; Y ii. a second group 252 'of an annular piercing element 252a'.

For ease of understanding, Figure 14 only shows the punch assembly 250 'and the metal sheet section 10'. Aungue. not shown in Figure 14, in use an annular region 15 'of the metal sheet 10' would be clamped during the spreading operation in an annular manner similar to the embodiment shown in Figures 13a and 13b.

In use, the first and second groups of puncher elements 251 ', 252' face the opposite surfaces of the enclosed portion 16 'of the metal sheet 10'. The spreading operation is performed by moving the first and second groups of the punch elements 251 ', 252' together to deform and extend (thin) the metal of the enclosed portion 16 '. The enclosed portion 16 'is deformed in an undulating profile 170' (see Figure 14).

In a further embodiment, a single extension punch 25 'has a number of relief features in the form of cavities / cuts 253' provided on its end face (see Figure 15). In the embodiment shown in Figure 15, there is a central cavity / cut surrounded by a single annular cavity / cut. However, alternative configurations of the cavity / cut can be used.

The embodiment in Figures 13a and 13b is shown piercing a single portion enclosed in a metal sheet section 10 '. However, the apparatus shown in Figures 13a and 13b can be used to extend and thin a plurality of enclosed portions 16 'spaced apart and placed through the area of the metal sheet 10'. Figure 16 shows the section of the metal foil 10 'which has undergone said paving operation to define a number of extended and thinned vaulted enclosed portions 16', 17 'placed across the area of the sheet. Although this has been done using a single spreading drilling machine by executing a number of successive spreading operations through the area of the metal sheet 10 ', it is preferred that the apparatus include a plurality of spreading drills which allows simultaneous spreading operations. are executed in a corresponding number of enclosed portions placed through the area of the metal sheet. However, to reduce the loads imposed on the tools used for spreading, it is beneficial to stagger any simultaneous spreading operations so that not all the portions enclosed by the sheet are extended at the same time. Figures 17a and 17b indicate six groups of enclosed portions - "a", "b", "c", "d", "e", and "f". In use, all the portions enclosed in each group would be extended simultaneously. In the embodiment shown in figure 17a, the extension would advance radially outwards from group "a" to group "b", group "c", group "d" to group "e", group "f". In the alternative modality shown in Figure 17b, the extension will advance radially inward from the group "f", to the group "e", to the group "d", to the group "c", to the group "b", to the group " to". Upon completion of the spread, separate preforms would be cut from the extended metal sheet for later stretching.

Note that Figures 16, 17a and 17b are illustrative only and are not intended to be to scale.

Initial stretch stage of the drawing operation, second illustrative method Upon completion of the paving operation, the metal foil 10 'with its extended and thinned vaulted enclosed portion 16', 17 'is moved to a take-up press 30'. The tucking press 30 'has a stretching pad 31' and a stretching die 32 '(see figures 18a and 18b). A drawing drill 33 'is co-axial with the drawing die 32', as indicated by the common axis 34 '. The stretcher 33 'is provided with a cavity 35'. A circumferential cutting element 36 'surrounds the stretching pad 31'.

In use, the metal sheet section 10 'is held in position between opposite surfaces of the stretching pad 31' and the stretching die 32 '. The sheet 10 'is located such that the domed enclosed portion 16', 17 'is centrally located above the hole of the stretching die 32'. After the metal sheet 10 'has been placed, the circumferential cutting element 36' is moved downwards to cut a preform 11 'of the metal sheet 10' (see Figure 18a). The excess material is indicated by 12 'in Figure 18a.

After the preform 11 'has been cut from the sheet 10', the stretching punch 33 'is moved axially downward to come into contact with the preform 11' (see Figure 18b). The stretching punch 33 'first contacts the preform 11' in an annular region 18a 'located adjacent and radially outward of the enclosed vaulted portion 16', 17 '(see figure 18a). The cavity 35 'provided in the stretching punch 33' prevents crushing of the enclosed vaulted portion 16 ', 17' during drawing. The stretching punch 33 'is continued to move downward through the stretching die 32' to progressively stretch the preform 11 'against the forming surface 37' of the die in the profile of a cup 19 'having a side wall 19' sw and integral base 19'b- However, the action of the stretcher 33 'against the preform 11' also causes material of the vaulted enclosed portion 16 ', 17' to be pulled out and transferred (as indicated by arrows D in Figure 18b). This initial stretching step results in a reduction in the height of the domed region because its material has been stretched outward. Depending on the depth of the stretch, the stretch may be sufficient to pull and transfer some of the stretched and thinned material from the enclosed vaulted portion 16 ', 17' to the side wall 19 'sw during this initial stretch stage, rather than this extended and thinned material remains completely within the base 19 'b. Figure 18b includes a separate view of the stretched cup 19 'which is the result of the use of the cupping press 30', with the domed region of reduced height at the base indicated by 17. "A detailed view is included in the figure 18a of the radius R'32 at the junction between the end face of the drawing die 32 'and its forming surface 37' As regards conventional drawing operations, the radius R'32 and the load applied by the Stretch pad 31 'to the periphery of the preform 11' are selected to allow the preform to slide radially inwardly between the opposite surfaces of the stretching pad 31 'and the drawing die 32' and along the surface of forming 37 'as the stretching punch 33' moves progressively downward to stretch the preform in the cup 19 'This ensures that the preform 11' is predominantly stretched, instead of being extended (thinned) (or worse, twisted around the crossing between the end face of the drawing die and the forming surface 37 '). Depending on the size of the radius R'32 and, to a lesser extent, the severity of the clamping load applied by the stretching pad 31 ', negligible stretching or thinning should occur during this initial stretching step. However, in alternative embodiments of the invention, it is permissible for the load applied by the stretching pad 31 'to be sufficient for a combination of stretching and additional stretching to occur under the action of the stretching punch 33'. The cup 19 'resulting from this initial drawing step is also referred to as the "first stage cup".

In an alternative embodiment of the invention which is not shown in Figures 18a and 18b, if the drawing depth were sufficient, this would result in the domed enclosed portion 16 ', 17' being pulled essentially flat in this drawing step. initial to define a cup 19 'having an essentially flat base 19'b- The cup of the first stage 19' resulting from the cupping process shown in figures 18a and 18b and described above is transferred to an assembly of body former 40, where re-stretching processes can be executed as previously described with respect to the extended cup 23.

Figure 19 shows the changes experienced by the metal sheet 10 'from before any training operations that have been experienced (view a), a after the paving operation in the paving rig 20' (view b), after of the initial drawing step in the take-up press 30 '(view c), and finally after the step of re-stretching in the body forming assembly 40 (view d). The figures clearly show that the base of the final cup has a reduced thickness (textendido) in relation to the incoming caliber of the metal 10 '(tenter), that is, texting < Tentering - As previously indicated, this reduced thickness (relative to the incoming caliper of the metal sheet) is enabled by the paving process of the invention. The effect of the initial stretching step on progressively pulling and transferring material out of the enclosed vaulted portion 16 ', 17' is shown in views b and c of Figure 19, with material at location X pulled and transferred outward to the location X 'as a result of the initial stretch stage. The effect of the re-stretching step is shown in view d of Figure 19, with material at location X 'pulled and transferred to location X "in side wall 19' sw.

To maximize the height of the side wall 19 'sw of the cup with its thinned base, the cup may also experience ironing of the side walls when being stretched through a succession of ironing dies (not shown) in an ironing operation. This ironing operation has the effect of increasing the height and decreasing the thickness of the side wall.

Figure 20 is a schematic view of a container 100 where either of the final resulting cup 19 '(or extended cup 23) serves as the body of the container 110. Preferably, the cup 19' (or extended cup 23) undergoes a process of conventional ironing (which is not shown in the figures) to achieve a desired lateral wall thickness. The container body 110 is flared outwardly in a rim 111 at its access opening. The can end 120 is provided with a seam panel 121 which allows the can end to be attached to the container body by sewing the rim 111. For analysis of the can or can body, the term "intermediate cup" refers to cups, such as 19 'or 23, which can be formed from the above methods, and the term "can body" refers to the structure of the cup after an ironing process.

Figure 21 is a graph of a material thickness distribution and Rockwell hardness distribution of an extended cup 123, which was prepared according to the first method (cup spread) described above from conventional tinplate (i.e. continuously annealed, T4) of 0.0110 inches (0.0279 centimeters) in thickness. Figure 22 shows a cross section of a can body base 124 after the re-stretching and ironing processes. The locations labeled on the base 124 correspond to the locations labeled in the cup 123 shown in Figure 21.

The base 124 includes a central, non-pearly, relatively flat panel 130 at its center, a taper or cavity 132 surrounding the lower panel 130., and a peripheral bead 134. Panel 130, cavity 132, and bead 134 together form a lower panel 140. Bead 134 produces an inward wall of a sausage bead 134, the bottom of which forms a vertical surface on which lies the can body. The top wall of the bead 134 preferably occurs smoothly to the side wall of the can body. Because the lower panel 40 is relatively unstructured, the base 124 can be considered non-domed.

The following information describes the cup 123 and the base 124 of the can body according to attributes of thickness distribution, hardness distribution, and micro-grain structure. Each aspect ratio value of thickness, hardness and grain provided herein depends on the incoming sheet thickness, the hardness, the annealing, the chemistry and the like, and depending on the desired attributes of the package, the desired degree of re-stretching, the final purpose of the container, and other well-known parameters. For thickness and hardness distributions, measurements are taken radially from the center along the grain direction, which is apparent from the laminate marks on the sheet. The values and ranges for aspect ratio of thickness, hardness and grain here provided, apply to the can body prior to any baking process, but also to the finished can body which is sewn together with one end.

As illustrated in Figure 21, the thickness of cup 123 decreases monotonically from 0.0097 inches (0.0246 centimeters) from the center at zero point to 0.0095 inches (0.0241 centimeters) at point 3, and increases to the point 8 near the boundary of the extended region of the cup. The numerical average thickness of the base extended from the zero center point to point 9 (near the edge of the extended dome) is 0.0099 inches (0.0251 centimeters) (an average thickness reduction of 9.8%), and an average thickness of the extended base from point zero to point 6 (which is the bottom panel 140) is 0.0096 inches (0.0243 centimeters) (a reduction of the average wall thickness of 12.2%).

The inventors conclude that any of the bottom panels of the can or the general extended portion of the cup, when formed of conventional tinplate, such as CA, plate TA, with a starting thickness of about 0.011 or 0.0115 inches (0.0279 or 0.02921). centimeters), can be formed in a range of thickness between 0.006 and 0.015 inches (0.0152 and 0.0381 centimeters), with greater preference between 0.008 and 0.010 inches (0.2032 and 0.0254 centimeters). The thickness reductions of at least 2%, preferably between 5% and 30%, more preferably between 10% and 25% are contemplated.

As expected due to the hardening of the work in relation to the paving process, the hardness values are inversely correlated to the thickness values. The Rockwell hardness number of the incoming raw sheet of 58 (RH T-30) is increased significantly through the extended region from points 0 to 9 to a minimum number of 63 (an increase of 8.6%) and a number average of 66 (an increase of 13.8%). For the lower panel 140, the minimum hardness number is 65 (an increase of 12.1%) and the average hardness number is 66.7 (an increase of 15.0%).

The inventors conclude that a hardness number can be achieved through the bottom of the can 140 of at least 63, preferably between 63 and 75, and more preferably between 64 and 70. In addition, the inventors conclude that the number of average hardness of the bottom of the can 140 preferably is at least 64, preferably 64 to 70, and more preferably 68. An increase in the average hardness number of the can bottom 140 of the incoming raw sheet of at least 5 on the RH scale, and with more particularity between 5 and 17, between 6 and 15, between 7 and 12, and between 8 and 10, it is believed that it can be achieved and is beneficial. The increase in the average RH number of the bottom of the can 140 is at least 7%, preferably between 8% and 21%, more preferably between 10% and 16%, and more preferably between 12% and 15%. As shown in Figure 21, the increase in the average Rockwell hardness number in the example is approximately 8 over the entire extended cup, and 8.7 in the bottom plate 140.

Figures 23 and 24 are photomicrographs of a cross section of polished and etched tin taken at or near the center of the respective can bottoms, generally in accordance with ASTM E 112 and in accordance with industrial practice. Figure 23 shows a cross section of a conventional tinned and pressed tin plate (CA, T4). Because conventional D I processes do not appreciably work the lower center of the can, it is believed that the micrograph of Figure 23 is very close to the structure of the incoming raw sheet. Figure 24 shows a cross section of a can formed according to the methods described above.

At the time of preparing the samples to identify grain boundaries, an aspect ratio of the grains can be identified by measuring the length of the grain in the rolling direction (ie, horizontally in the orientation of Figures 23 and 24) and dividing it by the grain dimension perpendicular to the direction of rolling (which is, vertically 'in the orientation of Figures 23 and 24). The inventors conclude that the average grain aspect ratio of a can body formed according to the present invention taken at the lower center of the central panel (corresponding to the zero point in Figure 22) is at least 1.4, preferably between 1.5 and 2.5, more preferably between 1.6 and 2.2. In the example of Figure 24, the average aspect ratio is approximately 1.8. The inventors conclude that the can body 124 will have an increase (compared to the raw sheet) of at least 20%, preferably between 20% and 100%, more preferably between 30% and 70%, and with greater preference between 40% and 60%. The averages can be taken by choosing the representative grains.

The above measurements provide an illustration of aspects of the present invention: other values and ranges herein are based on the inventors' estimates of achievable capabilities that are feasible from the technology described herein.

Claims (27)

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as a priority: CLAIMS

1. - A stretched and ironed metal can body adapted to be sewn onto a can end, the can body comprises: a ironed side wall; an enclosed, non-vaulted base integrally formed with the sidewall, a bottom panel of the base having an average Rockwell hardness number that is at least about 64.

2. - The can body according to claim 1, characterized in that the average Rockwell hardness number is between 64 and 70.

3. - The can body according to claim 2, characterized in that the average Rockwell hardness number is approximately 68.

4. - The can body according to any of the preceding claims, characterized in that the side wall has a thickness between approximately 0.006 inches (0.015 centimeters) and 0.015 inches (0.038 centimeters).

5. - The can body according to any of the preceding claims, characterized in that the side wall has a flange with the ability to be double stitched to a curvature of a can end.

6. - A stretched and ironed metal can body adapted to be sewn onto a can end, the can body comprises: an ironed side wall having a flange with the ability to be double stitched to a bend of a can end; Y an enclosed, non-vaulted base integrally formed with the side wall, the base having (i) a Rockwell hardness number that is at least about 65 or (ii) an average change in hardness of the raw sheet of at least 5 in number of Rockwell hardness or (iii) or an average change in Rockwell hardness number of the raw sheet of at least 7%.

7. - The can body according to claim 6, characterized in that the increase in the average Rockwell hardness number is between 5 and 17.

8. - The can body according to claim 6, characterized in that the increase in the average Rockwell hardness number is between 6 and 15.

9. - The can body according to claim 6, characterized in that the increase in the average Rockwell hardness number is between 7 and 12.

10. - The can body according to claim 6, characterized in that the increase in the average Rockwell hardness number is between 8 and 10.

11. - The can body according to claim 6, characterized in that the increase in the average Rockwell hardness number is between 8% and 21%.

12. - The can body according to claim 6, characterized in that the increase in the average Rockwell hardness number is between 10% and 16%.

13. - The can body according to claim 6, characterized in that the increase in the average Rockwell hardness number is between 12 and 15%.

14. - The can body according to claim 6, characterized in that the side wall has a thickness of between about 0.006 inches (0.015 centimeters) and 0.015 inches (0.038 centimeters).

15. - A stretched and ironed metal can body adapted to be sewn onto a can end and formed from a sheet of at least 0.105 inches (0.266 centimeters) in thickness, the can body comprises: a ironed side wall; a base integrally formed with the sidewall, the base includes a peripheral sausage and a substantially flat bottom panel, the bottom panel having an average thickness between 0.006 inches (0.015 centimeters) and 0.015 inches (0.038 centimeters), the lower panel has a reduction average in the thickness of the raw sheet of at least 2%.

16. - The can body according to claim 15, characterized in that the lower panel has an average reduction in the thickness of the raw sheet of between 5% and 30%.

17. - The can body according to claim 15, characterized in that the lower panel has an average reduction in the thickness of the raw sheet of between 10% and 25%.

18. - The can body according to claim 15, characterized in that the thickness of the average lower panel is between 0.008 and 0.012 inches (0.020 and 0.030 centimeters).

19. - The can body according to claim 15, characterized in that the average lower panel thickness is between 0.008 and 0.010 inches (0.020 and 0.025 centimeters).

20. - The tin body of stretched and pressed metal formed of tinplate, the body comprises: a ironed side wall; Y a non-domed base integrally formed with the side wall, the base includes a peripheral sausage and a lower wall radially within the sausage, grains in the base tinplate having an average aspect ratio of at least 1.4.

21. - The can body according to claim 20, characterized in that the average aspect ratio is between 1.5 and 2.5.

22. - The can body according to claim 20, characterized in that the average aspect ratio is between 1.6 and 2.2.

23. - The can body according to claim 20, characterized in that the average aspect ratio is approximately 1.8.

24. - The can body according to claim 20, characterized in that the average aspect ratio is at least 20% greater than the average aspect ratio of the raw sheet from which the can body is formed.

25. - The can body according to claim 20, characterized in that the average aspect ratio is between 20% and 100% greater than the average aspect ratio of the raw sheet from which the can body is formed.

26. - The can body according to claim 20, characterized in that the average aspect ratio is between 30% and 70% greater than the average aspect ratio of the raw sheet from which the can body is formed.

27. - The can body according to claim 20, characterized in that the average aspect ratio is between 40% and 60% greater than the average aspect ratio of the raw sheet from which the can body is formed.